Having a smartphone nearby reduces cognitive capacity, even when the phone is turned off, new research shows.

A team of investigators led by Adrian F. Ward, PhD, assistant professor, McCombs School of Business, University of Texas, Austin, conducted 2 studies in which close to 800 undergraduate students engaged in a cognitive task with their smartphones placed nearby and in sight, nearby and out of sight, or in a separate room.

The researchers found that the mere presence of a smartphone adversely affected available cognitive capacity, even when participants were successful at sustaining attention, were not using their phone, and did not report thinking about the phone. These cognitive effects were strongest in those who reported greater dependence on their smartphone.

“It’s not that participants were distracted because they were getting notifications on their phones,” said Dr Ward in a press release. “The mere presence of their smartphone was enough to reduce their cognitive capacity.”